1. Field of the Invention
The present invention relates generally to heat transfer elements and, more particularly, to heat transfer elements having thermally conductive fibers.
2. Description of the Related Art
It is well known that when two substances having different temperatures are brought together, the temperature of the warmer substance decreases and the temperature of the cooler substance increases. For example, when one takes a package of frozen meat from the freezer and places it on a counter to defrost, the temperature of the meat increases while the temperature of the counter and of the surrounding air decreases. Essentially, energy from the air and from the counter are being transferred to the meat to warm it. The temperature of the meat will continue to increase until its temperature equals that of the air and of the counter. At this time, the energy transfer ceases.
This energy or heat transfer can generally be broken into three basic categories: conduction, convection, and radiation. The transfer of energy by conduction occurs as a result of the presence of a temperature gradient within a fluid or solid. The transfer of energy by convection occurs between a fluid and a solid surface as a result of the temperature difference between the fluid and the solid surface. For instance, if the fluid is flowing through a passageway in the solid material that is cooler than the fluid, energy will be transferred from the fluid to the solid material, and the temperature of the fluid decreases. Lastly, the transfer of energy by electromagnetic waves is referred to as radiation heat transfer. Radiation heat transfer typically refers to energy transferred by thermal radiation between a solid surface and a gas or between two or more surfaces.
We take advantage of these thermodynamic properties every day, although we do not think much about it or are completely unaware of it. For instance, many devices that we rely on every day generate heat as a result of their operation. This heat generated by a device must be dissipated in order to maintain the device within a given operating temperature range so that it continues to function properly. One of the most common examples that demonstrates the three general categories of heat transfer is the automobile. The engine forms the heart of an automobile. As the engine operates, it generates heat that would quickly destroy the engine if the heat were not removed to maintain the engine temperature within a given range. The most common way to remove heat from an engine is to provide fluid passageways within the engine and to connect these fluid passageways to an external radiator, typically made from a metal such as aluminum, copper, or steel. As fluid circulates between the engine and the radiator, the radiator removes heat from the fluid and sends the cooler fluid back to cool the engine. The radiator transfers its heat energy to the air that passes over and surrounds the radiator.
Of course, it is understood that the radiator of an automobile is only one of many heat transfer elements currently in use. For instance, electrical parts, such as integrated circuits formed on semiconductor chips, also produce heat during operation. In most applications, metal heat sinks having fins are attached to these chips to remove heat from the chips. A fan is typically positioned to blow air over the fins so that energy from the heat sinks radiates into the large volume of air passing over the fins. However, in some more demanding applications, the electrical components may be coupled to a substrate, such as a ceramic substrate, that has a plurality of fluid passageways running throughout it. Much like the automobile's engine mentioned earlier, these fluid passageways are coupled to a heat transfer element, commonly called a radiator. The heated fluid passes into the radiator where it is cooled aid returned to the ceramic substrate to absorb heat from the electrical components.
Typically, electrical systems that require fluidic cooling are systems in which the electrical components are densely packed in an effort to reduce the size and weight of the electrical system. For instance, designers of electrical systems for satellites are primarily concerned with the size and weight of these systems. Of course, as automobiles are made smaller and lighter in order to preserve precious fuel and to comply with federal regulations, the size and weight of automobile radiators is also a concern. However, unlike the automobile industry, the satellite industry contains far fewer competitors. Thus, while high costs may prohibit the use of the smallest, lightest, and most efficient radiators in automobiles, the cost of a satellite's components is not so great a concern.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above by providing a novel and nonobvious heat transfer element.